Name: red algae pigments, shapes, and uses
Uploaded: 2025-06-12T09:26:52.000Z
Duration: 1 min 23 s
Channel: JoVE

Le alghe rosse o rodofite appartengono al Phylum Rhodophyta nel regno Archaeplastida.

Abitano gli ecosistemi terrestri, d'acqua dolce e marini.

Sono tipicamente caratterizzati dal loro colore rosso, che deriva dal pigmento ficoeritrina presente all'interno dei loro ficobilisomi.

Le alghe rosse sono fototrofiche e utilizzano principalmente la clorofilla per la fotosintesi.

Le alghe rosse unicellulari includono i generi Cyanidioschyzon e Galdieria. Prosperano a temperature comprese tra 30 °C e 60 °C e livelli di pH compresi tra 0,5 e 4,0.

Alcune specie di Galdieria possono persino crescere nella completa oscurità.

Cyanidioschyzon merolae ha un diametro di soli 1 o 2 μm e ha uno dei genomi eucariotici più piccoli di circa 16,5 coppie di megabasi.

Diverse specie di alghe rosse, come Polysiphonia, sono filamentose e multicellulari.

Alcune specie di alghe sono commercialmente apprezzate per la produzione di agenti addensanti, come l'agar e la carragenina.

Inoltre, le specie di Porphyra vengono raccolte, essiccate e utilizzate come involucri commestibili nel sushi.

principali phyla di alghe

Red Algae

Le alghe rosse, conosciute anche come rodofite, si trovano prevalentemente in ambienti marini, sebbene alcune specie vivano in ecosistemi d'acqua dolce e terrestri. Questi organismi esistono sia in forma unicellulare che multicellulare, con alcune variet&#224; multicellulari che raggiungono dimensioni macroscopiche.
In quanto organismi fototrofi, le alghe rosse contengono clorofilla a; tuttavia, i loro cloroplasti non contengono clorofilla b. Possiedono invece ficobiliproteine, pigmenti fotosintetici principali analoghi a quelli presenti nei cianobatteri. La tonalit&#224; rossastra di molte alghe rosse deriva dalla ficoeritrina, un pigmento accessorio che maschera il colore verde della clorofilla. Questo pigmento, insieme a ficocianina e alloficocianina, &#232; organizzato in strutture chiamate ficobilisomi, che fungono da antenne per la captazione della luce. Le specie che vivono in ambienti acquatici profondi tendono a produrre quantit&#224; maggiori di ficoeritrina, assumendo un aspetto rosso scuro, mentre quelle che abitano acque meno profonde ne hanno concentrazioni minori e possono apparire verdi.
La maggior parte delle alghe rosse &#232; multicellulare e priva di flagelli. Alcune variet&#224;, comunemente note come alghe marine, sono apprezzate per le loro applicazioni commerciali. Sono fonti di agar, un importante agente solidificante per i terreni di coltura microbiologica, e di carragenine, ampiamente utilizzate come agenti addensanti e stabilizzanti nell'industria alimentare. Alcune specie, come quelle del genere Porphyra, vengono raccolte, essiccate e utilizzate come involucri commestibili nel sushi. Morfologicamente, le alghe rosse possono presentarsi in forme filamentose o fogliacee, mentre altre, in particolare quelle che depositano carbonato di calcio, hanno un aspetto simile ai coralli. Queste alghe rosse coralline contribuiscono alla formazione e al consolidamento delle barriere coralline, rafforzandole contro l'erosione causata dalle onde.
Il genere Polysiphonia rappresenta un gruppo di alghe rosse filamentose e ramificate comunemente presenti negli ambienti marini di tutto il mondo. Questi organismi crescono prevalentemente in prossimit&#224; delle coste, ancorandosi a rocce, ad altre alghe e a superfici artificiali come moli, frangiflutti, banchine e strutture in cemento. Con quasi 200 specie riconosciute, Polysiphonia segue un ciclo riproduttivo complesso con alternanza di generazioni. Durante questo ciclo, i gameti maschili e femminili aploidi derivano da un organismo multicellulare diploide, maturando in individui multicellulari aploidi di entrambi i sessi. Le alghe maschili rilasciano cellule simili a spermatozoi aploidi, che si fondono con strutture riproduttive specializzate nelle alghe femminili, formando zigoti diploidi. Questi zigoti si sviluppano in organismi multicellulari che, a seguito della meiosi, rilasciano gameti maschili e femminili, completando cos&#236; il ciclo.
Oltre a specie multicellulari come Polysiphonia, alcune alghe rosse esistono in forma unicellulare. I membri dell&#8217;ordine Cyanidiales, inclusi i generi Cyanidium, Cyanidioschyzon e Galdieria, prosperano in ambienti estremi come sorgenti calde, acide e ricche di metalli. Questi organismi sopportano temperature comprese tra 30 &#176;C e 60 &#176;C e livelli di pH compresi tra 0,5 e 4,0, condizioni inospitali per la maggior parte degli altri microrganismi fototrofi, inclusi i fototrofi anossigenici.
Le alghe rosse unicellulari presentano diverse caratteristiche distintive. Ad esempio, Cyanidioschyzon merolae possiede cellule estremamente piccole, con diametro di soli 1&#8211;2 &#956;m, e uno dei genomi pi&#249; piccoli conosciuti tra gli eucarioti fototrofi, pari a circa 16,5 megabasi. Studi molecolari su Galdieria hanno rivelato che questa alga eucariotica ha acquisito almeno 75 geni tramite trasferimento genico orizzontale da diverse fonti procariotiche. Questi geni trasferiti conferiscono adattamenti quali resistenza allo stress salino, protezione contro la tossicit&#224; dei metalli e modificazioni che rafforzano la membrana citoplasmatica, permettendo la sopravvivenza in condizioni calde e acide. Inoltre, Galdieria possiede una capacit&#224; insolita di crescere in completa oscurit&#224;. Questa caratteristica &#232; legata a geni acquisiti orizzontalmente che codificano sistemi di trasporto per l&#8217;utilizzo di composti organici come fonti di energia.
Sebbene il trasferimento genico orizzontale sia tipicamente osservato tra organismi procariotici, il caso di Galdieria sottolinea il suo ruolo significativo nella formazione dei genomi microbici, anche attraverso differenti domini filogenetici.

Principali Phyla di Alghe

Le alghe rosse, conosciute anche come rodofite, si trovano prevalentemente in ambienti marini, sebbene alcune specie vivano in ecosistemi d'acqua dolce e ...

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red algae pigments, shapes, and uses

Red algae are phototrophic organisms found mostly in marine environments. Some species also live in freshwater or on land. They may be unicellular or multicellular, and some multicellular forms grow large enough to be seen easily.

These algae contain chlorophyll a, but their chloroplasts do not contain chlorophyll b. Instead, they use phycobiliproteins, which are light-harvesting pigments like those found in cyanobacteria. The red color seen in many species comes from phycoerythrin, an accessory pigment that hides the green color of chlorophyll. Phycocyanin and allophycocyanin also help capture light. These pigments are arranged in phycobilisomes, which act like antennae for light harvesting. Red algae from deeper water often make more phycoerythrin and appear darker red. Shallow-water species may have less of this pigment and can even look green.

Most red algae are multicellular and do not have flagella. Many seaweed species have commercial value. They are sources of agar, which is used to solidify microbiological culture media. They also provide carrageenans, which are used as thickening and stabilizing agents in food. Some red algae, such as members of the genus Porphyra, are harvested, dried, and eaten as sushi wraps.

Red algae can have different body forms. Some are filamentous, and others are leafy. Certain species deposit calcium carbonate and take on a coral-like look. These coralline red algae help form and strengthen coral reefs, where they add support against wave erosion. The genus Polysiphonia is a common example of filamentous, branched red algae found in marine habitats around the world. It often grows near shore and attaches to rocks, other algae, jetties, retaining walls, docks, and concrete surfaces.

Polysiphonia also shows a complex life cycle with alternation of generations. In this cycle, haploid male and female gametes come from a diploid multicellular organism and grow into haploid multicellular male and female individuals. The male algae release haploid sperm-like cells. These fuse with specialized reproductive structures on female algae to form diploid zygotes. The zygotes develop into multicellular organisms, and meiosis then produces male and female gametes again.

Not all red algae are multicellular. Some, including members of the order Cyanidiales such as Cyanidium, Cyanidioschyzon, and Galdieria, are unicellular and live in extreme hot, acidic, and metal-rich springs. They can survive temperatures from 30°C to 60°C and pH values as low as 0.5 to 4.0. Cyanidioschyzon merolae has very small cells, only 1 to 2 micrometers wide, and one of the smallest genomes known among phototrophic eukaryotes, at about 16.5 megabase pairs.

Studies of Galdieria show how gene transfer can shape survival. This alga has gained at least 75 genes from prokaryotic sources through horizontal gene transfer. These genes help with salt stress, metal toxicity, and membrane stability in harsh environments. Galdieria can also grow in complete darkness. That ability is linked to genes for transport systems that let it use organic compounds as energy sources. Its genome shows that horizontal gene transfer can be important even across different major groups of organisms.

Red Algae Pigments, Shapes, and Uses

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red algae

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key terms and concepts

Explore red algae pigments, body forms, commercial uses, reef-building species, alternation of generations, and extreme-environment unicellular forms.

Red Algae Pigments, Shapes, and Uses | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Red Algae Pigments, Shapes, and Uses

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